diff --git a/src/if_ruby.c b/src/if_ruby.c
index ce40bbe..818aacb 100644
--- a/src/if_ruby.c
+++ b/src/if_ruby.c
@@ -189,7 +189,9 @@
 #ifndef RUBY19_OR_LATER
 #define rb_num2long			dll_rb_num2long
 #endif
+#if defined(DYNAMIC_RUBY_VER) && DYNAMIC_RUBY_VER <= 19
 #define rb_num2ulong			dll_rb_num2ulong
+#endif
 #define rb_obj_alloc			dll_rb_obj_alloc
 #define rb_obj_as_string		dll_rb_obj_as_string
 #define rb_obj_id			dll_rb_obj_id
@@ -344,6 +346,17 @@
 {
     return dll_rb_int2big(x);
 }
+#if defined(DYNAMIC_RUBY_VER) && DYNAMIC_RUBY_VER >= 20
+VALUE
+rb_float_new_in_heap(double d)
+{
+    return dll_rb_float_new(d);
+}
+unsigned long rb_num2ulong(VALUE x)
+{
+    return (long)RSHIFT((SIGNED_VALUE)(x),1);
+}
+#endif
 #endif
 
 static HINSTANCE hinstRuby = NULL; /* Instance of ruby.dll */
@@ -434,7 +447,11 @@
 #endif
 #if defined(DYNAMIC_RUBY_VER) && DYNAMIC_RUBY_VER >= 18
     {"rb_string_value_ptr", (RUBY_PROC*)&dll_rb_string_value_ptr},
+# if DYNAMIC_RUBY_VER <= 19
     {"rb_float_new", (RUBY_PROC*)&dll_rb_float_new},
+# else
+    {"rb_float_new_in_heap", (RUBY_PROC*)&dll_rb_float_new},
+# endif
     {"rb_ary_new", (RUBY_PROC*)&dll_rb_ary_new},
     {"rb_ary_push", (RUBY_PROC*)&dll_rb_ary_push},
 #endif